Field of the Invention
The field of the invention relates generally to transmissions, and more particularly to methods, assemblies, and components for continuously variable transmissions (CVTs).
Description of the Related Art
There are well-known ways to achieve continuously variable ratios of input speed to output speed. Typically, a mechanism for adjusting the speed ratio of an output speed to an input speed in a CVT is known as a variator. In a belt-type CVT, the variator consists of two adjustable pulleys coupled by a belt. The variator in a single cavity toroidal-type CVT usually has two partially toroidal transmission discs rotating about a shaft and two or more disc-shaped power rollers rotating on respective axes that are perpendicular to the shaft and clamped between the input and output transmission discs. It is generally necessary to have a control system for the variator so that the desired speed ratio can be achieved in operation.
Embodiments of the variator disclosed herein include spherical-type variators utilizing spherical speed adjusters (also known as power adjusters, balls, planets, sphere gears or rollers) that each has a tiltable axis of rotation adapted to be adjusted to achieve a desired ratio of output speed to input speed during operation. The speed adjusters are angularly distributed in a plane perpendicular to a longitudinal axis of a CVT. The speed adjusters are contacted on one side by an input disc and on the other side by an output disc, one or both of which apply a clamping contact force to the rollers for transmission of torque. The input disc applies input torque at an input rotational speed to the speed adjusters. As the speed adjusters rotate about their own axes, the speed adjusters transmit the torque to the output disc. The output speed to input speed ratio is a function of the radii of the contact points of the input and output discs to the axes of the speed adjusters. Tilting the axes of the speed adjusters with respect to the axis of the variator adjusts the speed ratio.
There is a continuing need in the industry for variators and control systems therefor that provide improved performance and operational control. Embodiments of the systems and methods disclosed here address said need.